1. Field of the Invention
The field of the invention is automatic sample and reagent transfer and dispensing devices utilized with a centrifugal chemical analysis apparatus. More specifically, the invention relates to a cover for a sample tray which is utilized with the transfer and dispensing device wherein a liquid sample, such as blood plasma, is transferred from a sample cup to a chamber or well in a transfer disc which, when filled, is placed in the centrifugal chemical analysis apparatus for making a particular chemical analysis of the sample.
2. Description of the Prior Art
Centrifugal chemical analysis apparatus presently utilize a transfer disc having a plurality of channels arranged in a spoke-like configuration therein, each channel including at least three wells or chambers, one for receiving reagent, one for receiving sample and an outer well or chamber in which the sample and reagent are mixed during rotation of the transfer disc and then transferred to a reaction chamber where light is periodically passed through the reaction chamber to monitor the absorbance of the mixture each time a centrifuge device mounting the transfer disc rotates past a fixed position in the centrifugal chemical analysis apparatus.
In the use of the centrifugal chemical analysis apparatus it is first necessary to fill the reagent chambers with reagent and the sample chambers with different samples, such as blood plasma obtained from different patients. This is accomplished by placing the transfer disc and an annular sample tray on a turntable mounted on the table top of an automatic sample and reagent transfer and dispensing device.
The centrifugal chemical analysis apparatus can be of the type sold under the trademark ROTOCHEM by American Instrument Company, a division of Baxter Travenol Laboratories, Inc., of Silver Spring, Md., and the automatic sample and reagent transfer and dispensing device can be of the type sold under the trademark ROTOFILL by American Instrument Company, a division of Baxter Travenol Laboratories, Inc., of Silver Spring, Md.
The rotatable sample tray has an annular configuration with a plurality of sample cups mounted therein. The transfer disc and the sample tray are mounted on a turntable on the table top of the transfer and dispensing device on which are also disposed two arms extending respectively from two posts on the table top of the transfer and dispensing device and having aspirating or dispensing dip tubes at the outer ends thereof.
In the use of the transfer and dispensing device, the sample tray and transfer disc are indexed to rotate a sample cup to a sample pickup position, and the transfer disc to a reagent dispensing position, where a dip tube will pick up a given amount of sample, such as blood plasma, from a sample cup and then dispense that given amount of sample into a selected sample receiving well. At the same time a given amount of a selected reagent will be dispensed into a reagent well.
Oftentimes it is desirable to leave the sample tray on the table top for an extended period of time so that a plurality of tests can be performed on the blood samples, i.e., so that a number of transfer discs can be filled with sample and different reagents. However, evaporation of sample occurs and such evaporation affects the concentration of sample in the sample cups. Changes in concentration will affect the particular chemical analysis being made of the sample. Accordingly, it is desirable to provide some means for preventing evaporation.
As will be described in greater detail hereinafter the cover of the present invention solves this problem of evaporation by providing a simple cover for the rotatable sample tray which can easily and simply be placed over the sample tray to prevent evaporation of samples from sample cups which are not at the sample pickup station and which has means thereon to maintain the cover in a stationary position when the sample tray is rotated.